The present invention relates to film or sheet articles which have been converted into bags, pouches, etc., which a capable of providing a high strength, high abuse package for the packaging of a wide variety of industrial and consumer products. Such packages are subjected to high levels of abuse. The present invention is particularly directed to the use of such packaging for the direct mailing of various products, especially compact disks.
There are a wide variety of products which can benefit from being packaged in a high strength flexible film package, i.e., a flexible film package having a high tear resistance, a high burst strength, and/or other desirable characteristics which flow from the use of high strength, highly abuse-resistant packaging materials. High strength packages are resistant to puncture, tearing, failing seals, etc. Moreover such high strength flexible film packaging, due to the relatively small amount of material used in the package, can result in significantly less waste, hence less environmental impact (and easier recycling) than the more bulky alternatives such as wood crates, paper products (e.g., corrugated paper products), foams, etc. which are the most common forms of packaging where a high strength, abuse-resistant package is desired. The light weight and low bulk of such high strength flexible film packaging material also provides significant transport advantages over the more bulky packaging materials above, requiring less energy, to transport due to lighter weight, hence lower postage rates. Such packaging is also more tamper-evident and tamper-resistant than other forms of packaging, such as paper packaging. Moreover, high strength flexible film packaging products which are not reinforced with non-thermoplastic materials are more easily recycled than reinforced products, e.g., more easily than fiberglass reinforced plastic film packaging materials.
One high strength flexible film packaging material which has been in use for some time is marketed by Van Leer Flexibles, Inc. of Houston, Tex. i.e., VALERON(copyright) strength film. VALERON(copyright) strength film is made from high density oriented and cross-laminated polyethylene, and is stated as being puncture-resistant, tear-resistant, and chemical-resistant. VALERON(copyright) strength film is described as being strong, with a smooth surface. balanced tear-resistance, of uniform thickness, is printable with solvent-based and water-based inks, and is laminatable to paper, film, and other substrates. VALERON(copyright) strength film is also described as maintaining its properties in harsh environments and as having a temperature operating range of from xe2x88x9270xc2x0 F. to over 200xc2x0 F., and as being useful in the flexible packaging, shipping, construction, agricultural, photographic, and tag and label industries. VALERON(copyright) strength film is described as having much better tear resistance than single-ply film of the same overall thickness and of the same polymer which has been biaxially oriented. VALERON(copyright) strength film has also been stated to provide improvements over even other cross-laminated films because it is annealed, i.e., subjected to an elevated temperature (i.e., from 35xc2x0 C. to below the lowest melting point of the thermoplastic material present, excluding any adhesive or bonding layer). The annealing process reportedly provides VALERON(copyright) strength film with a higher impact strength relative to corresponding unannealed films.
However, VALERON(copyright) strength film is an expensive product relative to other films. This expense is undoubtedly due to the costs associated with both the cross-lamination and the annealing. It would be desirable to provide high strength flexible film packaging which has performance characteristics comparable to VALERON(copyright) strength film, but which is less complex to manufacture.
The present invention is directed to a high strength flexible film package which has characteristics comparable to packages formed from the cross-laminated films discussed above, but which is substantially less complex to produce. It has surprisingly been discovered that a non-crosslaminated film having a thickness of from 1 to 2.9 mils provides a package which is highly resistant to impact and burst, i.e., has a parallel plate burst strength of at least 190 inches of water. This high burst strength is unexpected in view of the film""s thin gauge, as well as it not being a cross-laminate, and even not necessarily being annealed. This thin, high strength film is simple and relatively inexpensive to produce, while providing a burst strength comparable to more complex and expensive cross-laminated, annealed packaging materials. Moreover, it has been further unexpectedly discovered that the package according to the present invention can utilize polyethylene copolymers, and hence substantially match the chemical-resistance, operating temperature range, and printability associated with cross-laminated, annealed flexible films.
As a first aspect, the present invention is directed to an article comprising a non-crosslaminated film which comprises at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, homogeneous ethylene/alpha-olefin copolymer, polycarbonate, polyester homopolymer, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ethylene/vinyl acetate copolymer, ionomer, ethylene/carbon monoxide, very low density polyethylene, low density polyethylene, polyolefin, ethylene/propylene copolymer, ethylene/norbornene copolymer, polystyrene, and ethylene/styrene copolymer. The non-crosslaminated film is bonded to itself or a second component which in turn comprises at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, homogeneous ethylene/alpha-olefin copolymer, polycarbonate, polyester, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ethylene/vinyl acetate copolymer, ionomer, ethylene/carbon monoxide, very low density polyethylene, low density polyethylene, polyolefin, ethylene/propylene copolymer, ethylene/propylene/diene terpolymer, ethylene/norbornene copolymer, polystyrene, and ethylene/styrene copolymer. The article has a parallel plate burst strength of at least 190 inches of water and a thickness of from about 1 mil to about 2.9 mils.
Preferably, the non-crosslaminated film is bonded to itself. Preferably, the film has a total thickness of from about 1.2 to 2.9 mils; more preferably, from about 1.2 to 2.8 mils. Preferably, the article has a parallel plate burst strength of from about 190 to 500 inches of water. The second component can be another film or any other object to which the non-crosslaminated film can be heat sealed or otherwise bonded or adhered. Although the film can be a monolayer film or a multilayer film, preferably the film is a multilayer film. Preferably, the film is a multilayer film comprising: (A) a first inner layer and a second inner layer, wherein each of the inner layers comprises at least one member selected from the group consisting of ethylene/vinyl ester copolymer, ethylene/vinyl acid copolymer, ionomer, and homogeneous ethylene/alpha-olefin copolymer having a density of from about 0.87 to 0.91 g/cc; and (B) a first outer layer and a second outer layer, wherein each of the outer layers comprises (a) at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, low density polyethylene, very low density polyethylene, homogeneous ethylene/alpha-olefin copolymer, olefin homopolymer, polycarbonate, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ester homopolymer, ionomer, ethylene/carbon monoxide copolymer, ethylene/propylene/diene terpolymer, ethylene/norbornene copolymer, and ethylene/styrene copolymer, as well as (b) at least one member selected from the group consisting of ethylene/vinyl ester copolymer, ethylene/vinyl acid copolymer, ionomer, and homogeneous ethylene/alpha-olefin copolymer having a density of from about 0.87 to 0.91 g/cc; and wherein at least one member selected from the group consisting of the first outer layer and the second outer layer is sealed to itself or the other outer layer. More preferably, the multilayer film has a total thickness of from about 2.3 to 2.7 mils, and wherein the article has a parallel plate burst strength of from about 300 to 500 inches of water.
Preferably, the multilayer film is heat-shrinkable. If heat-shrinkable, preferably the multilayer film is biaxially oriented and has a free shrink, at 185xc2x0 F., of from about 10 to 100 percent in at least one direction, i.e., the machine direction and the transverse direction. Alternatively or preferably, the film has a free shrink at 240xc2x0 F., of from about 20 to 80 percent in each of the machine and transverse directions; more preferably, from about 30 to 70 percent in each direction; still more preferably, from about 40 to 60 percent in each direction.
The film can further comprise an O2-barrier layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide polyester, polyacrylonitrile.
Preferably, the film is irradiated to a level of from about 50-150 kGy; more preferably, from about 75 to 125 kGy; still more preferably, from about 90-110 kGy; and, yet still more preferably, to about 100 kGy.
Optionally, or alternatively, the film may further comprise a crosslinked layer comprising a polymeric crosslinking enhancer, wherein the polymeric crosslinking enhancer comprises the reaction product of a polyene monomer and a C3 to C8 olefinic monomer. Optionally, a third monomer, different from the C3 to C8 olefinic monomer, can also be included in the polymeric crosslinking enhancer. This third monomer is selected from the group consisting of olefinic monomer, styrene or a styrene derivative, cycloolefin such as norbornene, unsaturated ester such as vinyl acetate; methyl acrylate, ethyl acrylate, and butyl acrylate, acid such as acrylic acid or methacrylic acid, and acid salt. The polymeric crosslinking enhancer can optionally be blended with another polymer. Alternatively, the polymer can be used alone. More particularly, the polymeric crosslinking enhancer comprises at least one member selected from the group consisting of ethylene/propylene/ENB terpolymer, ethylene/hexene/ENB terpolymer, ethylene/octene/ENB terpolymer, ethylene/hexene/5-vinylnorbornene terpolymer, and ethylene/octene/5-vinylnorbornene terpolymer.
Preferred forms of the article include an end-seal bag, a side-seal bag, an L-seal bag, pouch, and a backseamed casing.
As a second aspect, the present invention pertains to an article comprising a first multilayer film sealed to a second multilayer film, wherein: (A) a first multilayer film comprises at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, low density polyethylene, very low density polyethylene, homogeneous ethylene/alpha-olefin copolymer, olefin homopolymer, polycarbonate, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ester homopolymer, ionomer, ethylene/carbon monoxide copolymer, ethylene/propylene/diene terpolymer, ethylene/norbornene copolymer, and ethylene/styrene copolymer; and (B) a second multilayer film comprises at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, low density polyethylene, very low density polyethylene, homogeneous ethylene/alpha-olefin copolymer, olefin homopolymer, polycarbonate, polyamide, ethylene/acid copolymer ethylene/ester copolymer, ester homopolymer, ionomer, ethylene/carbon monoxide copolymer, ethylene/propylene/diene terpolymer, ethylene/norbornene copolymer, and ethylene/styrene copolymer. The first multilayer film is not a cross-laminated film and the second multilayer film is not a cross-laminated film. The first multilayer film has a thickness of from about 1 to 2.9 mils and the second multilayer film has a thickness of from about 1 to 2.9 mils. The article has a parallel plate burst strength of at least about 190 inches of water.
Preferably, the first multilayer film comprises two outer layers each of which comprises linear low density polyethylene, and two inner layers each of which comprises ethylene/vinyl acetate copolymer; and the second multilayer film comprises two outer layers each of which comprises linear low density polyethylene, and two inner layers each of which comprises ethylene/vinyl acetate copolymer. Preferably, the first multilayer film has a total thickness of from about 2.3 to 2.7 mils, the second multilayer film has a total thickness of from about 2.3 to 2.7 mils, and the article has a parallel plate burst strength of from about 300 to 500 inches of water, Preferably, the first multilayer film and the second multilayer film are identical with respect to chemical composition and thickness. Preferred articles include a pouch and a butt-sealed backseamed casing having a butt-seal tape. Optionally, the first multilayer film further comprises an O2-barrier layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, and polyacrylonitrile; and the second multilayer film further comprises an O2-barrier layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, and polyacrylonitrile. Preferably, the multilayer film is heat-shrinkable; preferably having a free shrink, at 185xc2x0 F. of from about 10 to 100 percent. Preferably, the film is irradiated to a level of from about 50-150 kiloGrays.
As a third aspect, the present invention is directed to a packaged product comprising a package and a product surrounded by the package, wherein the package comprises a non-crosslaminated film comprising at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, homogeneous ethylene/alpha-olefin copolymer, polycarbonate, polyester homopolymer, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ethylene/vinyl acetate copolymer, ionomer, ethylene/carbon monoxide, very low density polyethylene, low density polyethylene, polyolefin, ethylene/propylene copolymer, ethylene/norbornene copolymer, and ethylene/styrene copolymer. The non-crosslaminated film is sealed to itself or a second film comprising at least one member selected from the group consisting of linear low density polyethylene, high density polyethylene, homogeneous ethylene/alpha-olefin copolymer, polycarbonate, polyester, polyamide, ethylene/acid copolymer, ethylene/ester copolymer, ethylene/vinyl acetate copolymer, ionomer, ethylene/carbon monoxide, very low density polyethylene, low density polyethylene, polyolefin, ethylene/propylene copolymer, ethylene/propylene/diene terpolymer, ethylene/norbornene copolymer, and ethylene/styrene copolymer. The article has a parallel plate burst strength of at least 190 inches of water and a thickness of from about 1 mil to about 2.9 mils. The product comprises at least one member selected from the group consisting of compact disks, records, audio cassettes, video cassettes, tool, hardware, machinery parts, appliances, marine hardware, corrodable metal products, industrial parts containing rust inhibitor, aerosol spray can, wax, powdered chemicals, liquid chemical concentrate, industrial cartridge packs, toys, bearings, drywall, concrete board, bricks, dry pet food, adhesive, caulk, plaster mix, precut unassembled wood products, coffee, hops, shrimp, peanuts, retortable pouches, viscous fluids, explosives, frozen products, ballistic cargo, textile products, furniture, cars, boats, products dangerous for children, fertilizer and grain, plants, insecticide, sand bags (for flood control), water, seeds, skis, works of art, unmilled wood (especially firewood), lumber, tires, and hemmocult specimens.
There can be just one product in the package, or a plurality of products are in the package. The packaged product can further comprise a secondary packaging component between the film and the product, wherein the secondary packaging component comprises at least one member selected from the group consisting of rigid foam, flexible foam, film bubble product, and paper. Preferably, the secondary packaging component comprises foam. The foam can either be separate from the film, i.e., non-laminated to the film, or laminated to the film. Preferably, the foam comprises polyethylene. Preferably, the foam has a thickness of from 0.05 inch to 0.5 inch, more preferably from 0.05 inch to 0.2 inch.